Conventionally, for refrigeration apparatuses in which a plurality of outdoor units are connected in parallel to an indoor unit, operation methods have been proposed in which defrosting is performed in outdoor heat exchangers of some outdoor units to be defrosted, and the outdoor heat exchangers of the outdoor units are entirely defrosted while the units designated for defrosting are changed, as in, e.g., the air-conditioning apparatus disclosed in Patent Literature 1 (Japanese Laid-open Patent Publication No. 2008-25919).